Telescope Reviews: Re: Pairs of Doubles and Doubles within Clusters

Pairs of doubles

Struve 2470 and 2474 in Lyra,
The Double Double's double. Their separations of 13.4 and 16.2 respectively belie their difficulty. These are pretty faint pairs. 6.6-8.6/13.4" and 6.7-8.8/16.2" They were both seen as separated in 16x70 Fujinon's with difficulty.

Struve 2391 and HVI50 in Scutum,
Easy, both wide, both in the same low power view with M11 and the variable R Scutum.

Struve 232 and 6 Aries,
Easy, a mag8 double at 6.6" and a 3.9" double with color.
Stf 232, about one degree north east of 6 Tri, is 7.9-7.8/6.6". At 24x, all I could see was elongation, but with 20Tvplossls in the BT100 at 31x, this double was clearly split. 6 Tri is much closer at 5.3-6.9/3.9”, but is visible at 44x.

Struve 953 and Struve 954 in Monoceros
Struve 953 7.2-7.7/7.1" was an easy split with 25x100. It's about 1/2° south of the tip of the Christmas Tree cluster. In a 20x80 binocular I can only elongated this fairly even mag7 double. Struve 954 7.1-9.6/12.8" Although this one is much wider, it eludes the 25x100 binocs. I've tried many times but have not captured it at 25x. I had the BT100 set up with a 14mm radian giving 44x. The secondary of Struve 954 was even a little difficult for the BT100 at 44x.

Io (21) and Kappa (17) Bootes
Near the end of the handle of the Big Dipper. Io is 4.9-7.5/38” and kappa is 4.6-6.6/13.4”, not easy because of the 2 mag difference, but you can see it with a 15x70.

83 and 84 Leo
about 10° south of M65/M66. 83 is 6.2-7.9/28” and 83 is 5.1-8.0/91”

Gamma (12) Delphinus and Struve 2725
Gamma, 4.5-5.5/9.6” is an easy double for a 20x80, but will be difficult for a 15x70. Gamma Delphinus 9.6" has been cleanly split with 16x70 Fujinon. 2725 is a high-power pair at 7.6-8.4/5.8” that needs about 30x.

Alpha Capricorn is named Algedi. It follows Sagitarius, only is further north in declination. No simple double star, this one is a great one for giant binoculars! Algedi appears as a double-double in a 25x100 binocular. Both secondaries face south. The easy one is a1, on the right (west). It's a good try for most any binoculars. The left one (east), a2, is very close and faint and is a lot tougher. You folks with the giant binoculars and a little patience could see it.
It starts out, Alpha Cap, A, is a naked eye double.
A = a1 - a2. They are an easy naked eye double at 4.2-3.6/376".
a1 has components 4-9/45"
a2 has components 3.5-11/6.6"
a1 can be seen by most binoculars even down to 10x50. It's mag 9 secondary might get a little too faint for anything smaller than that. In very dark skies you could get it with something smaller.
a2 is not so easy. It's secondary is mag 11, so it needs at least a good 15x70 or a 16x70. But then, it's only 6.6" away from the mag 3.5 star. Now that's tough. That's makes the magnitude difference much more difficult, and the resolution more difficult. I've not seen any 6.6" doubles with even a good 20x80. The separation is too close. BUT, I've seen this one with my Oberwerk 25x100.

Double Stars within Open Clusters
Here’s the doubles culled out of my binocular list that all fall within open clusters. Many closer double’s are not included here since this list only went down to about 6” for binoculars to 25x.

The Trapezium, the famous multiple at the core of M42, is in the Orion nebula.

34 Cas, phi, AC 5.1-7.8/134”, the eyes of the Owl Cluster, in NGC 457

Stf 485, Cam 7.0-7.1/18”, 4h05m +61n, easy, in o.c. 1502

17 Com, 5.3-6.6/145”, in Mel 111, Berenices Hair

11 Lyr, Delta1, 5.6-9.3/175”, in Steph 1

B440, Cyg, probably seeing AF, 6.8-7.8/36”, 20h07m +36n, in o.c. 6871

Stf 2624, Cyg, AB is 7.2-7.8/1.7”, AB-C is 9.1/43”, 20h04m +36.5n, seen as 6.7-7.8/43”, in o.c. B146

56 And, 5.7-6.0/190”, on the edge of o.c. NGC 752

S 445, Per, 7.3-8.2/74”, 4h20m +50.5n, in NGC 1545

B536, Tau, AB-C, 8.1-8.0/39”, in the center of M45, The Pleiades

41 Ori, theta 1, Trapezium ABCD, A-B= 8.7”, A-C=12.9”, C-D=13.3”, B-D=19.2”

10 Mon, 5.1-9.3/77”, C=9.3/81”, BC= 9.3-9.3/21”, outstanding triple in o.c. 2232

Stf 1121, Pup, 7.0-7.5/7.4”, or 7.9-7.9/ 7.4" (SkyCatalogue2000), 7h38m –24s, easily separated at 25x, in o.c. M47,

There is a close pair at the center of M36, but I could not find a listing to identify it.
edit It's Stf 737 9.1-9.4/11"

39 Cnc, 6.5-6.5/150”, Aa=8.9/134”, Ab=9.2/135”, brightest stars in north core of M44

Sigma Mon (15 Mon) in o.c. 2264 the Christmas Tree cluster in Monoceros. Sigma Mon the base or trunk of the Christmas Tree, has eight components, widely spaced.

Struve 848 Ori in o.c. 2169 the Butterfly Cluster in Orion’s upraised arm

Stf 2816 is in o.c. IC 1396 in Cepheus. Both the great bright nebula and the open cluster within have the same designation.

edz

Edited by EdZ (07/19/07 05:50 AM)

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